linux原始套接字编程之收发链路层广播(发送端)



#include
#include
#include
#include

#include
#include

#include
#include
#include
#include

#include

#include

#define ETH_ALEN 6
#define ETH_P_GATE 0x9006
#define ETH_MAX_DATA_LEN 1488
#define ETH_HEAD_LEN 16
#define ETH_BODY_LEN 1496
#define ETH_LEN ETH_HEAD_LEN + ETH_BODY_LEN

struct EtherHead
{
 unsigned char   dest[ETH_ALEN];   /* destinat    ion eth addr */
 unsigned char   source[ETH_ALEN]; /* source e    ther addr    */
 unsigned int    proto;        /* packet type     ID field */
};

struct EtherBody
{
 size_t datalen;
 char data[ETH_MAX_DATA_LEN];
};

int Eth_SetHead(const char *destmac, const char *srcmac, int proto, struct EtherHead **head)
{
 char machex[6];
 int c,i;

 *head = (struct EtherHead *)malloc(sizeof(struct EtherHead));
 if(!*head)
 {
  return -1;
 }
 memset(*head, 0, sizeof(struct EtherHead));
 //填写帧头中的类型字段
 (*head)->proto=htons(proto);
 //填写帧头中的目的mac
 for (i=0;i<6;i++)
 {
  sscanf(destmac+3*i,"%2x",&c);
  machex[i]=(char)c;
 }
 memcpy((*head)->dest, machex, 6);
 //填写帧头中的源mac
 for (i=0;i<6;i++)
 {
  sscanf(srcmac+3*i,"%2x",&c);
  machex[i]=(char)c;
 }
 memcpy((*head)->source, machex, 6);
 return 0;
}

int Eth_CreatEth(void **eth, const char *data, size_t datalen, struct EtherHead *head)
{ 
 //帧数据部分
 struct EtherBody body;
 memset(&body, 0, sizeof(body));
 memcpy(body.data, data, datalen);
 body.datalen = datalen;
 //拼接帧(以太网中帧首部16字节，帧数据段最小46字节，FCS4字节，合计最小以太网帧长64字节)
 *eth = malloc(ETH_LEN);
 if(!*eth)
 {
  return -1;
 }
 memcpy(*eth, head, ETH_HEAD_LEN);
 memcpy((*eth) + ETH_HEAD_LEN, &body, ETH_BODY_LEN);
 return 0;
}

void Eth_Free(void **eth, struct EtherHead **head)
{ 
 free(*eth);
 *eth = NULL;
 free(*head);
 *head = NULL;
}

int main()
{
 //创建原始套接字
 int sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_GATE));
 if (0 > sock)
 {
  printf("create_sock err %s",  strerror(errno));
  return -1;
 }
 
 //获取网卡信息
 struct ifreq ifr;
 memset(&ifr, 0, sizeof(struct ifreq));
 memcpy(ifr.ifr_name, "eno16777736", strlen("eno16777736") + 1);
 ifr.ifr_ifindex = if_nametoindex(ifr.ifr_name);
 
 //填写发送信息
 struct sockaddr_ll sk_ll;
 sk_ll.sll_family = AF_PACKET;
 //sk_ll.sll_protocol = htons(ETH_P_GATE);//指定帧协议类型
 //sk_ll.sll_hatype = 1;
 sk_ll.sll_halen = ETH_ALEN;
 //sk_ll.sll_pkttype = PACKET_MULTICAST;//帧类型为链路层组播
 sk_ll.sll_ifindex = ifr.ifr_ifindex;//指定从哪个网卡发送帧
 
 //填写帧头
 struct EtherHead *head = NULL;
 Eth_SetHead("ff-ff-ff-ff-ff-ff", "00:0c:29:b5:15:a9", ETH_P_GATE, &head);
 //组装帧
 void *buf = NULL;
 Eth_CreatEth(&buf, "nihao", 5, head);
 //发出帧
 while(1)
 {
  if(-1 == sendto(sock, buf, ETH_LEN, 0, (struct sockaddr *)&sk_ll,  sizeof(sk_ll)))
  {
   printf("sendto err %s",  strerror(errno));
   exit(-1);
  }
  sleep(1);
 }
 //释放资源
 Eth_Free(&buf, &head);
}